REPORT OX ZOOLOGY. 



245 



Ehrenberg has rejected from the Infusoria several genera 

 which were formerly classed with these animals ; amongst others 

 the genus Vibrio, before spoken of as having been thought by 

 Duges and Blainville to show an affinity to some of the Entozoa. 

 It also appears probable from some of his observations, that 

 the genus Monas and several allied genera are not distinct ani- 

 mal forms, but only the young state of some Kolpodcs, Para- 

 mcpcia, &c. This idea has been subsequently adopted by 

 others*. 



Ehrenberg has since published a second memoirf, in which 

 he has extended his researches to several points of great intei'est 

 in the history of these animals. He has endeavoured to ascer- 

 tain the duration of Iheir existence, as well as the mode of their 

 development. He has also made some further discoveries with 

 respect to their structure. He has detected eyes (which before 

 he had only observed in some of the Rotatoria) in many of the 

 Polygastrica, and he has found them to furnish distinctive cha- 

 racters of great value in classification. He has fixed a nomen- 

 clature for all the principal external organs and appendages, 

 which he describes at much length. He has also made some 

 further remarks on the modifications of the alimentary canal, as 

 well as on those of the dental system. Since the date of his 

 first memoir he has found the teeth existing under several di- 

 stinct forms, and even ascertained their presence in some of the 

 Polygastrica. These discoveries have suggested some new 

 principles of arrangement. 



The above is a condensed abstract of the striking researches 

 made by this acute obsei'ver. We may judge what important 

 views they open to us, not only in respect to the structure of 

 these animals, but in respect to what may be the structure of 

 some other groups, in which also the organization has been con- 

 sidered hitherto as of the most simple kind. It is moreover not 

 improbable that they may ultimately help us in determining the 

 true limits of the animal and vegetable kingdoms, if between 

 them any fixed limits really exist. A complexity of structure, 

 of such a nature as is found in no vegetables, has been shovm by 

 Ehrenberg to exist in those forms which were formerly regarded 

 as very near the boundary; and although we now know of some 

 groups of a much more anomalous character than the Infusoria, 

 it is only extending our researches a little further, and we may 

 possibly be able to detect their real nature. There is one in- 



* See a paper entitled " Observations upon the Structure and Development of 

 the Infusoria," by Dr. Rudolph Wagner of Erlangen, in i\iG Edinb. New Phil, 

 Journ. for October 1832. 



+ Berlin Memoirs for 1831. 



